1. Field of the Invention
The present invention relates to a semiconductor light emitting device including semiconductor light emitting elements mounted on a flat substrate, and a method of manufacturing the same.
2. Description of the Related Art
LED lamps employing light emitting diodes can be realized with different light emission colors by a combination of light emitting diodes as an excitation light source and phosphors. Among methods of achieving a light emitting device that emits white color light, which is referred to as a white LED, there have been known a method of combining a light emitting diode that mainly emits blue color light and a yellow phosphor and a method of combining a light emitting diode that emits a near-ultraviolet ray, a blue phosphor, a green phosphor and a red phosphor.
In recent years, white LEDs have been employed as light sources of illumination systems, display systems and the like. However, in such employment of white LEDs, there remain issues of emission irregularity of light emitting elements themselves, emission irregularity caused by mounting such as wire bonding, etc., thus requiring improvement of characteristics of light emitting elements.
To avoid such issues, there has been known a technique of flip chip mounting without requiring wires disturbing an optical path and a technique related to a phosphor layer or a resin layer. See JP-A-2006-92983, JP-A-2005-276883, JP-A-2006-24615, JP-A-2004-80058, JP-A-2004-186488, JP-A-6-238884 and JP-A-8-99408.
Although a flip chip mounting used in a wide range has advantages of short wiring, good electrical property and a small mounting area over a wire bonding, the flip chip mounting has disadvantages of a complicated structure and high costs.
Techniques disclosed in JP-A-2006-92983 and JP-A-2005-276883 attempt to increase emission efficiency and provide uniform emission using unevenness formed in a phosphor layer. However, in the technique disclosed in JP-A-2006-92983, correction is not made based on emission irregularity of light emitting elements and also it can not be said that emission efficiency of all semiconductor light emitting devices are not necessarily increased. In addition, in the technique disclosed in JP-A-2005-276883, although thickness of a phosphor layer is changed based on emission irregularity of light emitting elements, since the phosphor is formed in combination with a second sealing resin member made in a different process, a manufacturing process is complicated.
In the technique disclosed in JP-A-2006-24615, unevenness is formed on a top surface using a print method to increase light output efficiency. However, the print method used herein is meant to be a stencil print method to require a stencil plate, so it is difficult to make correction to irregularity of individual semiconductor light emitting devices. In addition, in the technique disclosed in JP-A-2006-24615, although unevenness may be formed in a lateral side in addition to the top surface, it is difficult to maintain high precision of unevenness due to friction which may occur when semiconductor light emitting devices are peeled out of a stencil plate.
In techniques disclosed in JP-A-2004-80058 and JP-A-2004-186488, a light emission state is measured, and correction is made to irregularity of individual semiconductor light emitting devices using a liquid droplet discharging apparatus. However, a surface mounting LED package shown herein, which is a combination of a cup-shaped substrate and a resin filler, has disadvantages of requirement of substrate processing, complicated processes, and high costs. In addition, JP-A-2004-80058 and JP-A-2004-186488 disclose only an application to cup-shaped LEDs, but do not show a detailed application to a flat substrate.